Radioactive junkyards remain dangerous for millennia. So how do you keep future generations of urban explorers and dumpster divers away from all that toxic trash? With a sign, of course!

New Mexico’s Waste Isolation Pilot Plant (WIPP) may be the trashiest place on Earth. Buried deep in the Chihuahuan Desert, the plant contains nearly 2 million cubic feet of radioactive sludge and debris leftover from various nuclear weapons and defense projects. But don’t mistake the WIPP for a simple pit in the ground. Scientists at the U.S. Department of Energy spent nearly 20 years carefully planning the safest way to throw out the country’s nuclear trash before committing to the site.

Today, the plant resides inside a 250 million-year-old salt deposit that’s positioned half a mile underground. And there’s good reason for that. Scientists chose the location because of its ability to prevent radiation from contaminating groundwater and seeping out to the surface. Because salt deposits tend to slowly collapse on themselves over time, scientists are banking on the idea that the structure will naturally seal in the nuclear waste, safely entombing the site deep underground.

Under the WIPP’s current charter, the site will continue to receive radioactive garbage from the country’s nuclear weapons and energy programs until about 2070—at which point it will be sealed up and never opened again. At least, that’s the plan. The WIPP still has one major problem, though. Radioactive waste remains dangerous to humans for at least 10,000 years. So, how do we tell people living in the far distant future to stay out of our trash? The government’s solution: some good, old-fashioned warning signs.

Global Warning

Of course, coming up with such a simple plan wasn’t all that easy. To keep future generations safe, the U.S. government had to do some seriously long-term thinking. In the 1990s, when the WIPP was still being completed, federal officials convened a panel of scientists, anthropologists, and linguists to brainstorm. And just to ensure they had enough diverse minds involved, they also invited a team of science-fiction writers to join the mix.

The group realized early on that big “Do Not Enter” signs wouldn’t suffice for the WIPP site. After all, they reasoned, there were plenty of curses and warnings carved into the ancient pyramids to ward off grave robbers, and clearly, legions of Egyptologists ignored the pictograms and raided the tombs anyway. What’s more, it’s doubtful that folks 10,000 years from now will even be able to read modern English. Think of it this way: Only a few of today’s scholars can understand the original Beowulf without a translation, and that text is only 1,000 years old.

Creating an ominous warning sign that lasts forever and translates for generations across all cultures wasn’t going to be easy. But as Germany learned when it faced a similar problem in the 1980s (thanks to some leaky nuclear-storage incidents), academics aren’t shy about offering out-of-the-box suggestions. One expert proposed writing a message on an artificial moon and launching it into space. Because the moon would always be visible in the night sky, the warning would be impossible to forget. Yet another expert proposed creating an “atomic priesthood”—an elite class of people who would protect the area from one generation to the next by scaring the public with veiled threats of a supernatural curse. On the opposite end of the spectrum, one researcher suggested leaving the site entirely unmarked, reasoning that human curiosity is too powerful a force
to overcome.

But the strangest suggestion by far came from two German linguists. They argued that governments around the world should breed cats that turn colors when exposed to radiation. These so-called “ray cats” could then be immortalized in song and legend, so that even after the scientific knowledge of radiation had been lost to the sands of time, folklore would tell of their supernatural power to change their fur in the presence of extreme danger.

For the time being, the U.S. government has settled on a much simpler idea. Surrounding the WIPP will be a forest of concrete obelisks, etched with messages in multiple languages, including English, Chinese, Spanish, Latin, Hebrew, and Navajo. The structures will also contain a series of pictograms that depict human faces in pain. Admittedly, it sounds a whole lot like the warnings on the Egyptian pyramids. But fortunately, the government still has time to come up with a different plan. The WIPP site won’t be sealed for at least another 60 years—and that’s plenty of time to breed a ray cat.

This story originally appeared in a 2011 issue of mental_floss magazine.